Currently, as a core technology of a transport network, an optical transport network (OTN) includes technical specifications of an electrical layer and an optical layer, has abundant operation, administration and maintenance (OAM) capabilities, a strong tandem connection monitor (TCM) capability, and an out-of-band forward error correction (FEC) capability, and can implement flexible scheduling and management of a large-capacity service.
For an electrical processing layer, an OTN technology defines a standard encapsulation structure, and the standard encapsulation structure is used to implement mapping of various client services, so as to manage and monitor a client signal. An OTN frame structure is shown in FIG. 1. An OTN frame is a structure of 4×4080 bytes, that is, 4 rows×4080 columns. The OTN frame structure includes a framing area, an optical channel transport unit overhead (OTU OH), an optical channel data unit (ODU) OH, an optical channel payload unit (OPU) OH, an OPU payload area, and an FEC area. Herein, 16 head columns are overhead bytes, 256 tail columns are FEC check bytes, and 3808 intermediate columns are payloads.
An OPUk is used to adapt to a client signal, and includes an OPU payload area and an OPU OH, and k represents a rate level of an OPU. When k=1, 2, 3, and 4, k is respectively corresponding to fixed rate levels of 2.5 G, 10 G, 40 G, and 100 G. There are two fixed tributary slot granularities: 1.25 Gbit/s and 2.5 Gbit/s that are distinguished based on a payload type PT overhead. When PT=0×21, it denotes, a tributary slot granularity is 1.25 G. When PT=0×20, it denotes tributary slot granularity is 2.5 G. When k=flex, that is, an OPUflex, the OPUflex is corresponding to any rate level, has no tributary slot, and carries only a single service. When k=Cn, that is, an OPUCn, the OPUCn is corresponding to a rate level that is n times 100 G, and has only one fixed tributary slot, that is, 5 G. A payload type PT of the OPUCn is 0×22. An ODUk is used to support an information structure of the OPUk. The information structure includes information about the OPUk and an ODUk OH. Capacities of the ODUk are distinguished based on k. An OTUk includes the ODUk, the FEC area, and an OTUk OH. As service traffic increases and requirements are diversified, while bandwidth increases, a transport network has gradually evolved from a fixed pipe to an elastic pipe, for example, a lower order ODUflex bearer container or an OTUCn of n times 100 G. Especially, for the OTUCn of n times 100 G, a frame structure of the OTUCn includes n OTN frames (excluding the FEC area), and a tributary slot granularity corresponding to the OTUCn is 5 Gbit/s.
In the prior art, a conventional ODUflex is applied to only a single service, and carries and transports the single service in a fixed mapping manner.
Specifically, as shown in FIG. 2, a constant bit rate (CBR) service is mapped to the ODUflex by using a bit synchronous mapping procedure (BMP), and is then transported by using a higher order ODUk or an ODUCn. For a packet (PKT) service, when the packet service is less than or equal to 100 G, the packet service is mapped to the ODUflex by using a generic framing procedure (GFP), and is then transported by using the higher order ODUk or the ODUCn. When the packet service is greater than 100 G, the packet service is mapped to the ODUflex by using an idle mapping procedure (IMP), and is then transported by using the higher order ODUk or the ODUCn.